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For a more sustainable food future, molluscs and small fish may be the answer

A new study finds that oysters, scallops, anchovies, and sardines aren't just delicious: they may be our best bet for a sustainable, protein-rich diet.
June 15, 2018

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Want to substantially reduce your environmental footprint? Consider switching red meat for molluscs and tiny forage fish like anchovies, a new study suggests.

The new Frontiers in Ecology and the Environment study ranked common animal-based foods like beef, pork, and chicken, pelagic fisheries, molluscs, and catfish aquaculture according to their planetary impact. Across factors like greenhouse gas emissions, energy-use and eutrophication, it showed that beef–unsurprisingly–had the highest environmental footprint. More unexpectedly, farmed catfish came in as a close second.

On the flipside, the study found that farmed molluscs and small pelagic fish like anchovies and sardines captured out at sea were the most sustainable dietary options, overall.

As the researchers weighed up the impacts of each food type, they made some especially surprising discoveries. Not least was the fact that livestock farming was less energy-intensive on average than most forms of aquaculture and deepsea fisheries (with the exception of mollusc farming and small pelagic fisheries). This came down to the fact that fishing vessels tend to guzzle huge amounts of fuel when they’re out at sea. Aquaculture also relies on high quantities of fuel to power machines that keep the water circulating within fish pens.

Pelagic fisheries were an exception to this rule, the researchers found, because these small fish form huge schools out at sea that can be captured efficiently–providing higher amounts of protein per quantity of fuel consumed. Molluscs had low energy requirements too, because the water in their pens doesn’t need to be circulated.

When it came to greenhouse gas emissions, beef and catfish produced the highest–some 20-fold more than small pelagic fish and molluscs. This came down to the soaring levels of greenhouse gas-emitting fertilizers that are used to grow the huge quantity of plant-based feed–such as soy pellets–that’s part of the dietary regime for cows, and some farmed fish. Again, molluscs and pelagic fisheries had the lowest emissions impact: farmed molluscs don’t require feed, and fertilizers obviously aren’t required for fishing out at sea.

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Fertilizer use is also a major driver of eutrophication, the nutrient pollution of rivers, lakes, and the sea. So animal products that relied on more fertilizer–like beef–scored higher here, too. But interestingly, pork and chicken production had a lower eutrophication impact than some forms of aquaculture, like shrimp and tilapia, which may rely on high quantities of plant feed.

Across all these factors, small pelagic fisheries and molluscs consistently had the lowest footprint, underscoring their potential as a particularly sustainable protein source. 

The researchers came to these conclusions by reviewing 148 studies that each did a life-cycle analysis (LCA) for one animal-based food. Because these LCAs looked at everything from energy use, to greenhouse gas emissions, eutrophication, and multiple other factors, the researchers had a huge database to draw upon. To rate each food type, they measured the impact of one 40 gram serving of protein in each case.

Animal-based food consumption is expected to rise in coming decades, in line with a growing population and increasing world income, the researchers write. So, finding ways to meet our hunger for protein with as little impact as possible has become more crucial than ever. The study suggests that for seafood lovers, this could be very good news.

Source: Hilborn et. al. “The environmental cost of animal source foods.” Frontiers in Ecology and the Environment. 2018.
Image: via MaxPixel

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